The invention relates generally to controlling fuel flow in a fuel injection system, and more particularly to an apparatus for preventing flow of fuel to the intake manifold via the manifold vacuum passage.
Most port or throttle body fuel injection systems include a fuel pressure regulator which controls the fuel pressure supplied to the fuel injectors. The pressure regulator may be a diaphragm-operated relief valve in which one side of the diaphragm is subject to liquid fuel pressure and the other side is subject to intake manifold vacuum. The nominal fuel pressure is established by a spring preload applied to the diaphragm. Varying the force on one side of the diaphragm with manifold pressure maintains the desired fuel pressure at the injectors. Fuel in excess of that used by the engine is bypassed through the regulator and returned to the fuel tank.
A problem, recognized by the inventor herein and not addressed in the prior art, is that should the fuel/vacuum barrier established by the diaphragm be breached, relatively high pressure liquid fuel would be delivered to the intake manifold through the manifold vacuum passage. Under such conditions, the increased fuel-to-air ratio would cause the engine to run rich of stoichiometry.